Possible roles in cancer development, autoimmune conditions, and infection have also been articulated.[11] These roles are owed to different characteristics such as increased hydrophobicity, size and hydrogen bonding compared to Neu5Ac due to the presence of the additional acetyl functional group.[12] Expression of Neu5,9Ac2 has also been observed in cancer cells.[13] Neu4,5Ac2 is only expressed in certain vertebrates such as monotremes,[14] guinea pigs[15] and horses[16] where it plays roles in disrupting bacterial and viral activity. This evidence concerns the gene NEU4 and cancer.